Clearance angle gauge



1953 c. G. GASE 2,648,138

CLEARANCE ANGLE GAUGE Filed Nov. 7, 1947 2 Sheets-Sheet 1 VENTOR. CARLGASE C. G. GASE CLEARANCE ANGLE GAUGE Aug. 11, 1953 2 Sheets-Sheet 2Filed Nov. 7, 1947 INVENTOR. CARL G. GASE WM, w

' angle relative to the radius of the tool.

Patented Aug. 11, 1 953 CLEARANCE ANGLE GAUGE Carl G. Gase, Macedonia,Ohio, assignor to The Weldon Tool Company, a corporation of OhioApplication November 7, 1947, Serial No. 784,543

1 Claim.

The invention relates to tool gauges having a fixed mount to hold thepiece to be gauged.

An object of the invention is to accurately gauge the critical back-offclearances for the cutting edge of a cutting tool.

Another object of the invention is to provide a gauge which may beaccurately positioned relative to a tool edge to be gauged, and themeasurement multiplied for easy reading.

A still further object of the invention is to provide a gauge to gaugethe clearance angle or angularity of the surface which defines thebackoff clearance for the cutting edge of a cutting tool.

Cther objects and a fuller understanding of the invention may be hadbyreferring to the following description and claim, taken in conjunctionwith the accompanying drawing, in which:

Figure 1 is a perspective view of the gauge;

Figure 2 is an enlarged view of a flute and cutting edge of an end millwith the gauging contact face of the gauge member in contact therewith;1

Figure 3 is a diagrammatic illustration of the scale and gauge member,aligned with the axis of the tool to be gauged;

Figure 4 is a view similar to Figure 3 with th gauge member in contactwith the surface to be gauged, the back-01f surfaces being exaggeratedfor illustration;

Figure 5 is an alternate type of gauge member;

Figure 6 is yet another alternate type of gauge member and scale alignedwith the work piece;

Figure '7 is a View similar to Figure 6 with the work piece rotated tocontact the surface to be gauged with the gauge member;

Figure 8 is a sectional view as indicated by line 8-8 of Figure 1; and

Figure 9 is a sectional view as indicated by line 9-9 of Figure 1.

It is difiicult to check spiral work and very narrow back-off angles,which are necessary on small diameters. Prior to this invention,however, there has been no practical means to determine the clearanceangle accurately, because of the extremely small dimensions.

The'double back-off of a tool which may be gauged by this tool gauge isbest illustrated in Figure 2 of the drawings. The double back-offconsists of a first back-off surface H extending from the cutting edge52 rearwardly at a slight angle relative to the radius of the tool, anda second back-off surface 69 extending at a greater To the naked eye,the back-01f surface H is too small i is .018 inch wide.

to discern the width thereof, let alone measure the angle thereof. Forexample, in a one inch end mill, the back-off surface I l extends at an8 angle with respect to a radius of the tool, and Although it isdesirable to have the back-off surface 49 held within reasonable limits,the'angle of the back-off surface ll relative to a radial line of thetool passing through the cutting edge 52 is highly critical and is thedetermining factor for the amount of work which the tool willaccommodate. Also in Figure 2 the undercut side 4! of the individualcutting flute may be seen.

It is often the case in the early development of a particular art orscience, that certain developments are known to contribute to theworthiness of the science, but often it is not realized at first howextremely critical the limits imposed upon the use must be. Back-offclearances have been used in all types of cutting tools, including theend mill type of tool. It has only recently been discovered that theangle of the first back-off clearance extending from the cutting edge ishighly critical, and that if this angle is held exactly to the correctexact small fraction of a degree, that the production of the tool willbe increased 50 per cent or more over the production ability when thefirst back-off clearance is allowed to vary even a fraction of a degreeaway from the optimum angle for the given tool. Further, various angleshave been found to produce optimum results for various metals. In someinstances the best angle is found by test experience. -When once thebest clearance angle'has been found, it is essential to provide thatexact angle on tools produced thereafter, and with this gauge, it ispossible to repeat the best clearance found by experience. Many reasonsmay be attributed for this phenomenal increase in cutting ability due tothe exact back-off clearance, but the fact remains that regardless oftheory the increase in production can readily be determined by actualshop practice, and in fact has been proven many times over in shoppractice.

Of course, an angle that is so critical cannot be ground freehand.Grinding machinery must be employed, and even the results of the machinemust be closely observed inorder to dress the grinding stone and adjustthe machine in order to keep the angle perfect. Prior to the developmentof the present invention, the development of a perfect back-offclearance has been dependent upon the skill of the craftsman grindingthe cutting flute and back-off clearances, or has been left to merechance because of a lack of the understandin of the necessity forobtaining such close accuracy in the back-off clearance angle.

This invention will gauge the angle of the back-off surfaces relative tothe radius of the tool with an accuracy well within the limits ofaccuracy permissible. In the Figure 1 of the drawing, the gauge for theclearance angle of the back-off surface of a tool is illustrated inperspective in order to show the relationship of the various parts. Inthe Figure 1, the reference character 20 illustrates a bed or base forthe gauge. It is desirable that the bed 20 be rather heavy in order thatthe gauge wil1.not easily move and therefore require the operator toholdthe device while in use.

The Figure 8 is a sectional view through the Figure 1 as indicated bythe line 8-8 of Figure l, and illustrates the construction of several ofthe cooperating parts. .In the Figure 8, it will be seen that a dovetailway'26 is provided on top of the bed 20. A carriage 25 including a'dovetall 21 and a slide 23 is mounted to reciprocate longitudinallyrelative to the bed 20. In the particular adaptation of the invention asillustrated, a rack 30 extends longitudinally of the dovetail way 26.Arod 32 is carried by the carriage 25, and is provided with a piniongear 3I adapted to operate with interlocking teeth with the rack 30. Aknob 33 is secured to the end of the rod 32 and serves as a finger gripto rotate the rod 32 and the pinion gear 3|. The carriage 25 may therebybeactuated longitudinally in a forwardly or rearwardly direction byturning the knob 33 in the direction in which it is desired to move thecarriage25. The carriage 25 is provided with a way 29 in the .form of alongitudinal groove. The slide 28 is provided with a longitudinal ridge48 complementary to the way 29 whichis adapted to guide the slide 28 forlongitudinal movement relative to the dovetail 21. Thus, the carriage 25may be actuated to a desired'position, and the slide thereafter movedrelative to the .carriage 25 for further longitudina1 adjustment. Inother words, the adjusting knob .33 .is used for rough adjustments inorder to accommodate various sizes of tools, and theslide'28 thereafterused for fine adjustments relative to the cutting edge of the tool.

In Figure 9 of the drawings, a cross-sectional view of the tool mount I3of the gauge is illustrated and'includes a vertical bore I4 in the bed20. A guide bearing I5 is .held in the upper portion of the bore I4. Amounting insert I6 is adapted to closely interfit with the internalsurface of the guide bearing I5, and isadapted to hold a bushing I9therein. Grip prongs I 1 extend radially about the upper portion .of themounting insert I6 and are used as .fingergrips to turn the mountinginsert I6 in theguide'bearing I5. A look screw I8 is provided to extendthrough the guide bearing I5 and hold themounting insert IS in aselected position. The bushing I9 has an outside diameter to fit theinternal diameter of the mounting insert I6, and .hasan internaldiameter to fit the shank of a tool] 2. In other words, the bushing I9compensatesfor various sizes of shanks. In some instances the tool I2may have a shank large enough to fit directly into the internal diameterof the mountin insert I6, and therefore the bushing I9 would not berequired. In most instances, however, a bushing I9 will be required tohold the tool I2 in the mounting insert I6. Thus, the tool I2 may be '4rotated about its longitudinal axis with the axis extending in onedirection, and the slide 28 will be longitudinally reciprocable in asecond direction at an angle to the direction in which the tool extends.

The carriage 25 serves as a positioning means to mount a gauge memberfor longitudinal reciprocation in the second direction at an angle tothe direction in which the tool extends. In the Figures 1, 3 and 4, agauge member 2I is illustrated, and in Figure 5 of the drawings an.alternate type gauge member 22 is illustrated.

The Figures 6 and '7 illustrate the third type of gauge member 23 andthe use thereof.

In .the Figure 1, it will be seen that the gauge member .-2 I includes agauge body 50 having a gauging contact face 5| and a pointer arm 24.Ascale 35-is attached to the surface of the slide 28, and serves toindicate the change of position of the pointer arm relative to thescale. The gauge member 2| is pivoted to the surface of the slide 28 bya pivot 36 in the form of a screw or rivet. The pivot 36 is positionedon the slide 2-8'ito -lie on-a line extending from the longitudinal axisof the tool I2 to a point on the scale 35. (See .centerline *53 inFigure 2.) words,-=if a line wereextended from a point on the scale 35(and normally that point would be the 'zero point in the center of ascale), to the longitudinal axis of the workpiece I 2, the line wouldconstitute a radius of the tool, and the pivot 36 would lie exactly onthat line. Thus, the-zero mark on the scale 35 and the pivot 36 whichserves as a pivotal mounting means for the gauge member, define astraight line passing through the longitudinal axis of the tool I2.Furthermore, the gauging contact face 5| in the preferred embodiment ofthe invention is perpendicular to the longitudinal axis of the pointerarm 24. Therefore, the longitudinal axis of the pointer arm 24 may bealigned to extend coextensively with'the radial line from the zero markof the scale through the longitudinal axis of rotation of the tool I2.In the Figure 1, and in the Figure 2 ,*a hairline 46 is marked upon thesurface of the gauge body 50. This visual hairline 46 is employed as anindicator to align the cutting edge of the tool I2 with the line 53extending from the zero mark on the scale 35 to the longitudinal axis ofthe tool I2.

To operate the preferred embodiment of the invention'in the formillustrated in Figure l of the drawings, the tool I2 is mountedconcentricallyin the tool mount I3 illustrated in Figure 9. Thelongitudinal axis of the tool I2 and the axis-of'rotation produced bythe mount I3 should be identical. That is, the tool I2 is mounted torotate about its longitudinal axis. The gauge member 2I is then pivotedto place'the end of the pointer arm 24 exactly on the zero position ofthe scale 35. Thus, the gauging'contact face'5I will be positionedperpendicular to a radial line of the tool I2. The carriage 25 is thenmoved to within a relatively close distance of the tool I2 by turningthe knob 33 and actuating the carriage 25 toward the tool I2.Thereafter, the slide 28 is manually adjusted relative to the tool I2 tocomplete the gauging action. A finger-grip portion 34 on the slide 28 isprovided to aid in the -manual adjustment of the slide 28. The gaugingcontact face 5| is brought close to the cutting edge 52 of the tool I2,and the tool I2 is rotated in the tool mount I3 to position the cuttingedge 52 into exact alignment with the hairline 46, as best illustratedin Figure 3. In other In other words, the zero mark, the pivot 36, andthe cutting edge 52 are all aligned on the radius line 53 of the tooll2.

After the tool and gauging member 2| are perfectly aligned asillustrated by the full lines of Figure 2, the gauge member 2| ispivoted to place the gauging contact face 5| into contact with theback-off surface H as indicated by the dotted lines in Figure 2. Theangle of the surface II to be measured is the angle between theperpendicular to the radius of the tool extending through the cuttingedge, and the back-off surface II. It will clearly be seen that thisangle is represented by the angle 60 of Figure 2. The second back-offangle is indicated by reference character 62. Therefore, when the gaugemember 2| is pivoted and longitudinally repositioned to place thegauging contact face 5! into contact with the back-off surface II, theangle 6| between the original setting of the pointer arm 24 and thefinal position of the pointer arm 24 will represent the angle 60 whichis to be measured. The angle 6| may be determined directly from thescale 35. Of course, the arm 24 magnifies the angle many times, andtherefore is easily determined from the scale.

As before indicated, the angle 60 is extremely critical and thereforemust be provided within close limits if optimum results are to beobtained from the tool. These angles have been determined for aparticular size and type of tool. Therefore, after the back-01fclearances II on each of the flutes have been ground, they are measuredby the process steps which have been described, and if the angle 60 iscorrect, the tool is passed on for use, but if the angle 60 isincorrect, the grinding operation is repeated until it is brought withinclose limits.

The land width of the back-off surface is quite small. Therefore, it isvirtually impossible to produce a correct positioning between the gaugemember 2| and the back-off surface with the naked eye. Accordingly, Ihave provided a magnifying eye-piece 38 positioned at an angle to theaxis of the tool, and a spotlight 39 to light the area underobservation, which when magnified will appear enlarged as illustrated inFigure 2. The angular position of the eye-piece 38 permits inspection ofthe gauging of spiral flutes. A spiral flute would interfere with topobservation. A transformer 40 is located within the bed and current iscarried from the transformer 40 to the spotlight 39 by means of asuitable wire 43. Thus, a bright, small spotlight may be provided toilluminate the gauging area, and the clearance surface H and gaugingcontact face 5| will be enlarged. An inlet plug 4| is provided on theside of the bed 20 for convenience in attaching the gauge to anysuitable outlet, and a switch 42 is adapted to connect and disconnectthe transformer 40. By these useful additions to the gauge, the operatormay align the cutting edge 52 exactly with the hairline 46, and will beable to position the gauging contact face 5| in full contact with theback-off surface I Accordingly, by the magnification of the gaugingprocess, the limits of inaccuracy are held extremely low.

In the Figure 5, I illustrate a gauge member 22 having a fixed gaugingcontact face 44. The gauge member 22 is adapted to operate in the way 29on the carriage in place of the slide 28. By this method, the gaugingcontact face 44 may be provided at exactly the angle desired. Therefore,by moving the gauge member 22 into contact with the back-off surface II, and by placing the cutting edge directly in contact with the hairlineon the gauge member 22, the operator can tell immediately whether theback-01f surface H has been ground at too great or too small an angle,or if the angle is exactly correct. Of course, by this method ofgauging, the operator cannot tell exactly what the angle of the backoffsurface I actually is, but he can tell whether or not it is correct ashe desires it.

In the Figures 6 and 7, a third method of employing the basic conceptionof the invention is illustrated. In the embodiment illustrated therein,the mounting insert I6 is provided with a convenient marker on the sidethereof as indicated, and a rotary gauge on the surface of the bed 20 isprovided around the mounting insert I6. Therefore, the tool may berotated and the radial movement indicated by the scale and marker. Agauge member 23 is employed with this method of gauging and is adaptedto move in the way 29 in place of the slide 28. However, the gaugemember 23 is provided with a gauging contact face 45 at a -degree anglerelative to the radius of the tool, and the longitudinal axis of thegauge member 23. Therefore, the cutting edge 52 of the tool 2 may bealigned with the hairline of the gauge member 23, and the toolthereafter rotated as indicated in Figure 7 to bring the back-offsurface into contact with the gauging contact face 45. Thus, it willreadily be seen that the scale on the surface of the bed 20 may beemployed to determine the radial rotation, and therefore may be scaledto read directly in degrees and portions of degrees to ascertain theclearance angle of the back-01f surface II. In each instance, thecontact between the tool and the gauge surface may be observed throughthe eye piece 38 in order to assure measurement within close limits.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

I claim as the invention:

A gauge for measuring the clearance angle between a radius lineextending through a spiral cutting edge and a back-01f surface of arotatable tool, said gauge comprising, a base providing an axis line anda radius line transversely intersecting said axis line, said base havinga cylindrical opening concentric with said axis line, a carriage movablealong said radius line on said base towards and away from said axis lineand the cylindrical opening, a gauge member pivoted for angularpositioning on said carriage and pivotally positionable in at least afirst and a second position relative to said radius line, said gaugemember providing a straight edge line extending at an angle to said axisline and also providing a sight line transversely bisecting saidstraight edge line, said gauge member when in said first positionpositioning said sight line in a common plane with said radius line andsaid axis line, said gauge member when pivoted to the second positionpositioning said sight line outside of said common plane, a tool mounttube rotatably and removably slidable in said cylindrical opening withthe axis of the tool mount tube coextensive of said-axis lineto-holdvarspiraledged cutting tool concentrically slip fitted'thereinand with antitt1ng=edgec1ose to and ata spaceddistance from saidstraight edge line and in sight extending alignment with said sight linewhen the sight line isin said-commoncplane, said carriage and said-basehavinganinterassooiatedrack and gear operable to move the'carriagetowards the axis line'when the gauge member is pivoted to the secondposition with thesaid edge line close to and parallel \to the back-ffsurface of the tool and'with the-sight line out of said common plane andat an angle :to the first vposition directly representing the clearanceangle of the tool.

CARL G. GASE.

References "Cited in theme of this patent UNITED STATES PATENTS NumberNumber Number Name Date Webster Nov. 2, 1920 Toomey Sept. 11, 1923Steinle Apr. 8, 1924 Romig Sept. 15, 1925 Harter June 15, 1926 GillettOct. 16, 1928 Becker July 20, 1943 Spedding Jan. 30, 1945 GeissbuehlerJan. 30, 1945 FOREIGN PATENTS Country Date France May 18, 1942 FranceJune 1, 1942 France Aug. 24, 1942 France Oct. 1, 1945

